1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, and in particular to a method of manufacturing a semiconductor device having a reliable capacitor.
2. Description of the Background Art
In recent years, demand for semiconductor devices have been increased due to remarkable popularization of information devices such as computers. It has been required for such a semiconductor device, as for the function thereof, to have a large-scale memory capacity and an ability of operating at a high speed. Accordingly, technological developments have been in progress for higher integration, faster responsiveness, and higher reliability.
In a capacitor of a Dynamic Random Access Memory (hereinafter referred to as xe2x80x9cDRAMxe2x80x9d) a three-dimensional structure and a rough-surfaced structure have been employed in order to secure a capacitance. A DRAM in which the rough-surfaced structure is applied in a cylindrical capacitor will be described below.
Referring to FIG. 20, a well implant layer 102 and isolation insulating films 103 are formed on a P-type silicon substrate 101. Thereafter, Polysilicon films 106a, 106b, silicide films 107a, 107b and insulating films 108a, 108b are respectively formed, with gate insulating films 105a, 105b interposed, on a region between isolation insulating films 103.
Drain regions 104a, 104b and 104c are respectively formed, for example, by introducing an impurity with an ion implantation method, using insulating films 108a, 108b and so forth as masks. Side wall insulating films 109a, 109b are respectively formed on side surfaces of polysilicon films 106a, 106b, silicide films 107a, 107b and insulating films 108a, 108b. Thus, gate electrodes including polysilicon films 106a, 106b and silicide films 107a, 107b are respectively formed.
An inter-layer insulating film 110 is formed on silicon substrate 101 by CVD (Chemical Vapor Deposition) method so as to cover the gate electrodes. A bit-line contact hole 110a which exposes the surface of source/drain region 104b is formed on the inter-layer insulating film 110. A polysilicon film 111, a silicide film 112 and an insulating film 114 are formed in bit-line contact hole 110a. A side wall insulating film 115 is formed on the side surfaces of polysilicon film 111, silicide film 112 and insulating film 114. Thus, a bit line 113 including polysilicon film 111 and silicide film 112 is formed.
An inter-layer insulating film 116 is further formed on inter-layer insulating film 110 so as to cover bit line 113. Storage node contact holes 116a, 116b, respectively exposing the surfaces of source/drain regions 104a, 104c are formed in inter-layer insulating films 116 and 110. Polysilicon plugs 117a and 117b are respectively formed to fill in storage node contact holes 116a and 116b. 
An inter-layer insulating film 118 is further formed on inter-layer insulating film 116. Openings 118a, 118b respectively exposing the surfaces of polysilicon plugs 117a, 117b are formed on inter-layer insulating film 118. Thereafter, a polysilicon film 119 is formed on inter-layer insulating film 118 including the side and bottom surfaces of openings 118a, 118b. A rough-surfaced polysilicon film 120 is formed on poly-silicon film 119.
Referring to FIG. 21, a photoresist 121 is applied to rough-surfaced polysilicon film 120. Next, referring to FIG. 22, the entire surface of photoresist 121 is etched to remove photoresist 121 located above the top surface of inter-layer insulating film 118 and to leave photoresist 121 only in openings 118a, 118b. 
Referring to FIG. 23, for example, by dry etching, for example, polysilicon film 119 and rough-surfaced polysilicon film 120 exposed on the top surface of inter-layer insulating film 118 are removed. Thereafter, as shown in FIG. 24, photoresist 121 that has been left in openings 118a, 118b is removed. Thus, storage nodes 122a, 122b including polysilicon films 119a, 119b and rough-surfaced polysilicon films 120a, 120b are respectively formed. A dielectric film 123 is then formed on rough-surfaced polysilicon films 120a, 120b. 
Referring now to FIG. 25, a cell plate 124 including, for example, a polysilicon film is formed on dielectric film 123. An inter-layer insulating film 125 is formed so as to cover cell plate 124. A predetermined aluminum interconnection 126 is formed on inter-layer insulating film 125. Thus, the main part of the DRAM is completed.
However, a problem as described below lies in the above-described method of manufacturing a semiconductor device. When storage nodes 122a, 122b of the capacitor are formed, polysilicon film 119 and rough-surfaced polysilicon film 120 located above inter-layer insulating film 118 are removed by dry etching in the step shown in FIG. 23.
This may make the top end portions of storage nodes 122a, 122b be pointed as shown in FIG. 26, which may degrade the reliability of dielectric films to be formed thereupon. As a result, the reliability of the capacitor may be deteriorated. Moreover, the pointed portions of storage nodes 122a, 122b may be broken off in the subsequent processes, causing a pattern defect, which would disadvantageously lower the yield.
Further, a process of increasing the particle size of a rough-surfaced polysilicon film may be employed in order to secure the capacitance of the capacitor. In such a case, as shown in FIGS. 27 and 28, an amorphous silicon film 131 is formed, with a relatively thin insulating film 130 interposed, on a polysilicon film 129.
Thereafter, by a predetermined thermal process, amorphous silicon film 131 is made rough, forming a rough-surfaced polysilicon film 132, as shown in FIG. 29. It is noted that insulating film 130 would disappear by the thermal process. Through such a process, particles of rough-surfaced polysilicon film 132 will be increased in size. In such a case, however, adhesiveness between rough-surfaced polysilicon film 132 and polysilicon film 129 is insufficient so that the particles of rough-surfaced polysilicon film 132 may be separated from the surface of polysilicon film 129. Thus, the capacitance of the capacitor may not be sufficiently secured, which would lower the reliability of the capacitor.
The present invention is directed to solve the problems described above. It is an object of the present invention to provide a method of manufacturing a semiconductor device in which a reliable capacitor is secured.
The first aspect of the method of manufacturing the semiconductor device according to the present invention includes the steps below. An insulating film is formed on a semiconductor substrate. An opening is formed in the insulating film. A conductive layer is formed on the insulating film including side and bottom surfaces of the opening. A coating layer is formed on the conductive layer including an inner side of the opening. A predetermined removal process is performed on the coating layer and the conductive layer that are located on the insulating film, to make a top end of the conductive layer lower than a top surface of the insulating film to form a first electrode portion. A second electrode portion is formed, with a dielectric film interposed, on the first electrode portion.
This manufacturing method makes the top end of the conductive layer lower than the top surface of the insulating film in the step of forming the first electrode portion, so that the top end portion of the conductive layer will not protrude from the top surface of the insulating film, and thus breakage of the top end portion can be prevented, while no residue or the like of the conductive layer is left and the conductive layer on the insulating film is completely removed. This suppresses generation of pattern defects and forms the first electrode portion with high reliability, improving the reliability of the capacitor including the first electrode portion, the dielectric film and the second electrode portion.
Preferably, the predetermined removal process in the step of forming the first electrode portion includes a first step for removing the coating layer and the conductive layer at a substantially same rate so that a top surface of the insulating film and surfaces of the coating layer and the conductive layer exposed at an opening end of the opening are aligned, and a second step for removing a portion of the conductive layer located adjacent to the opening end of the opening, substantially leaving the insulating layer.
In this case, the top surface of the insulating layer and the surfaces of the coating layer and the conductive layer, exposed at the opening end of the opening, can easily be made coplanar by the first step, so that the protrusion and breakage of the top end portion of the conductive layer can be prevented. Further, the residue of the conductive layer or the coating layer on the insulating film can be completely removed by the second step.
It is also preferable that the first step includes a step of removing the coating layer and the conductive layer located on a top surface of the insulating layer by a chemical mechanical polishing method.
In this case, the top surface of the insulating layer and the surfaces of the coating layer and the conductive layer that are exposed on the opening end surface of the opening can be aligned.
It is further preferable that the first step includes a step of removing the coating layer and the conductive layer under an atmosphere including CF4 and excess O2.
In this case, the top surface of the insulating film and the surfaces of the coating layer and the conductive layer that are exposed on the opening end of the opening can be aligned by a commonly-used etching device, not necessarily using a chemical mechanical polishing device.
More preferably, the second step includes a step of removing the conductive layer in an atmosphere of gas including CF4 and O2.
In this case, only the conductive layer can easily be etched without substantial etching of the insulating film, and hence the top end of the conductive layer can be made lower than the position of the top surface of the insulating film.
Preferably, the method of manufacturing a semiconductor device includes a step of removing the insulating film located on an outer side of the first electrode portion after forming the first electrode portion and before forming the dielectric film.
In this case, in addition to an inner surface of the first electrode portion, an outer surface of the first electrode portion may be overlapped with the second electrode portion, advantageously increasing the capacitance of the capacitor.
The second aspect of the method of manufacturing the semiconductor device according to the present invention includes the steps below. A first electrode portion is formed on a main surface of a semiconductor substrate. A second electrode portion is formed, with a dielectric film interposed, on the first electrode portion. The step of forming the first electrode portion includes steps of forming a first layer, forming spots that will be an insulating layer on the first layer, forming a second layer on the insulating layer, and performing a thermal process to the second layer for roughening the surface thereof.
According to this manufacturing method, adhesiveness between the roughened second layer and the first layer is improved to eliminate a possibility that the second layer is easily separated from the first layer, so that reliability of the semiconductor device including a capacitor having the first electrode portion, dielectric film and the second electrode portion is improved.
Preferably, the step of forming the insulating layer includes a step of forming by a chemical oxidation method.
In this case, the insulating layer is grown as spots at an early stage of the growth of the insulating layer on the first layer.
To specify the types of the films, the first layer includes a polysilicon film, and the second layer includes an amorphous silicon film.